Cathode Bypass Caps: E'lytic vs. non-polar

18watt-specific Tech Talk - Building, Fixing, Parts, Mods...

Moderators: Daviedawg, Graydon, CurtissRobin, colossal, zaphod_phil

Post Reply
ViperDoc
Occasional poster
Occasional poster
Posts: 135
Joined: Mon 05/18/20 8:09 pm

Cathode Bypass Caps: E'lytic vs. non-polar

Post by ViperDoc »

Couple of questions:

1) What's the difference between using electrolytic vs. non-polarized radial caps on a preamp tube cathode to ground?

2) As the voltages on preamp tube cathodes is usually low, a 50V-rated cap would be enough, yes?

Thanks.
0 x

User avatar
TriodeLuvr
Occasional poster
Occasional poster
Posts: 120
Joined: Tue 10/16/18 11:19 am

Re: Cathode Bypass Caps: E'lytic vs. non-polar

Post by TriodeLuvr »

ViperDoc wrote:
Wed 01/13/21 10:51 pm
Couple of questions:

1) What's the difference between using electrolytic vs. non-polarized radial caps on a preamp tube cathode to ground?

2) As the voltages on preamp tube cathodes is usually low, a 50V-rated cap would be enough, yes?

Thanks.
Electrolytic caps are used to provide the necessary capacitance in a physically small package. If the value is small enough, say 1uF or less, a film cap can probably be used. Preamp cathodes typically only charge to a few volts. I've seen 10V and 15V caps in some circuits.

Jack
1 x

ViperDoc
Occasional poster
Occasional poster
Posts: 135
Joined: Mon 05/18/20 8:09 pm

Re: Cathode Bypass Caps: E'lytic vs. non-polar

Post by ViperDoc »

I read that Electrolytics are claimed to be "slower" than film caps, but I'm not sure how that affects tone. Preamp sag?
0 x

geoff 1965
Frequent poster
Frequent poster
Posts: 856
Joined: Mon 01/04/16 3:52 pm

Re: Cathode Bypass Caps: E'lytic vs. non-polar

Post by geoff 1965 »

i've got a wima 3.3uf polyester on the cathode in one of my amps and the tone/detail is superb but quite different to the higher value electrolytics.if you notice the low value poly/films are used a lot where the triode cascades into another to cut bass and keep a clearer signal.read the notes on ZP's lite2 cascade mod in the downloads and experiment yourself,you will tell the difference.
1 x

ViperDoc
Occasional poster
Occasional poster
Posts: 135
Joined: Mon 05/18/20 8:09 pm

Re: Cathode Bypass Caps: E'lytic vs. non-polar

Post by ViperDoc »

Thanks, I'll check that out.
0 x

Post Reply